What is the recommended approach to sedation in patients with head injury?

Sedation in Head Injury

In patients with head injury requiring sedation, use continuous infusions of propofol or benzodiazepines (midazolam) as first-line agents, maintaining adequate cerebral perfusion pressure ≥60 mmHg while avoiding bolus dosing and hypotension. 1, 2

Primary Sedation Strategy

Propofol is the preferred agent for sedation in head-injured patients due to its ability to decrease intracranial pressure (ICP) by 46% while maintaining mean arterial pressure, and it demonstrates preserved flow-metabolism coupling. 3 The FDA label confirms propofol controlled ICP while maintaining cerebral perfusion pressure in neurosurgical ICU patients. 3

Propofol Dosing and Administration

• Initiate at 27 mcg/kg/min (mean maintenance rate across ICU studies), with a range of 2.8-130 mcg/kg/min titrated to effect 3
• Lower doses required in patients >55 years: approximately 20 mcg/kg/min versus 38 mcg/kg/min in younger patients 3
• Use continuous infusion only—never bolus doses, as boluses cause decreased blood pressure and compromised cerebral perfusion pressure 4, 3
• Monitor with processed EEG (such as BIS monitoring) when neuromuscular blockade is used to ensure adequate depth of sedation 1, 2

Critical Propofol Precautions

• Expect 15-20% decrease in blood pressure during initiation, particularly in the first 60 minutes 3
• Have vasopressors immediately available (phenylephrine or norepinephrine) rather than relying on fluid resuscitation alone 4
• Large doses (>4 mcg/mL plasma concentration) impair cerebrovascular autoregulation from 54% to 28%, potentially increasing vulnerability to secondary insults 5
• Contraindicated in pediatric ICU sedation due to increased mortality (11% vs 4% with standard sedatives) 3

Alternative Sedation Options

Midazolam (Benzodiazepines)

• Comparable efficacy to propofol with similar S100beta markers of neurological injury and equivalent neurological outcomes at 3 months 6
• Causes moderate decrease in cerebral metabolic rate and ICP with generally negligible side effects 1, 7
• May decrease mean arterial pressure through reduced central sympathetic drive, requiring blood pressure monitoring 7

Dexmedetomidine (Emerging Alternative)

• Dosing range: 0.2-1.0 mcg/kg/hr without initial bolus, or with bolus of 0.8-1.0 mcg/kg over 10 minutes 8
• Similar hemodynamic safety profile to standard sedation with transient bradycardia and hypotension episodes 8
• May reduce agitation episodes and alleviate sympathetic hyperactivity symptoms 8
• Allows for neurological assessment due to anxiolytic properties without deep sedation 8

Analgesia Management

Use continuous infusions of opioids—never bolus dosing—as bolus administration causes arterial hypotension catastrophic in TBI patients. 4

Opioid Selection and Dosing

• Fentanyl is first-line: causes hypotension in only 1.6% of trauma patients 4
• Morphine alternative: hypotension rate 0.5% but higher nausea/vomiting (4.8%) 4
• All opioid infusions require continuous blood pressure monitoring to maintain systolic BP >110 mmHg 4

Adjunctive Analgesia

• Intravenous acetaminophen every 6 hours is effective and used in 78% of TBI patients at discharge 4
• NSAIDs use with extreme caution due to acute kidney injury and gastrointestinal bleeding risks 4
• Ketamine may be considered (0.5% hypotension rate) but requires additional sedation 4

Absolute Contraindications

• Tramadol is absolutely contraindicated: reduces seizure threshold in patients already at high risk for post-traumatic seizures 4
• Mixed agonist-antagonist opioids (pentazocine, nalbuphine, butorphanol) precipitate withdrawal 4

Sedation Management Principles

Standard ICU Guidelines Apply with Modifications

Follow standard ICU sedation protocols for non-brain injured patients, except when treating intracranial hypertension or status epilepticus. 1, 2

• Daily interruption of sedation is potentially harmful in TBI patients with signs of high ICP on CT scan, as it may cause ICP elevation and cerebral metabolic stress 1, 2
• Light sedation protocols from general ICU populations do not apply during targeted temperature management or when controlling ICP 1
• Pain assessment using Behavioral Pain Scale (BPS) when patients cannot self-report with Numeric Rating Scale 1

Hemodynamic Targets During Sedation

Maintain cerebral perfusion pressure (CPP) ≥60 mmHg at all times, as even single episodes of hypotension (SBP <90 mmHg) markedly worsen outcomes. 2, 4

• Target systolic blood pressure >110 mmHg continuously 4
• Manage hypertension by increasing sedation first, then small boluses of labetalol 1
• Treat hypotension after correcting hypovolemia or excess sedation with alpha-agonist bolus followed by infusion (metaraminol or norepinephrine via central line) 1

Ventilation Parameters

• Target PaCO2 4.5-5.0 kPa (34-38 mmHg) during routine management 1
• Target PaO2 ≥13 kPa (≥98 mmHg) to avoid even brief hypoxic episodes 1
• Use PEEP 5-10 cmH2O: minimum 5 cmH2O prevents atelectasis, up to 10 cmH2O does not adversely affect cerebral perfusion 1

Management of Raised ICP During Sedation

First-Tier ICP Control

• Head of bed elevation 20-30° to assist venous drainage 1, 2
• Bolus of sedative drugs (propofol or midazolam) as immediate intervention 1
• Maintain adequate sedation and analgesia following protocols with modifications for ICP control 1, 2

Second-Tier ICP Control

• Mannitol 0.5 g/kg infused over 15-20 minutes 1, 9
• Hypertonic saline 2 mL/kg of 3% saline (250 mOsm) over 15-20 minutes 1, 9
• Temporary hyperventilation (PaCO2 not less than 4 kPa/30 mmHg) only for impending herniation as bridge to definitive therapy 1, 2

Common Pitfalls to Avoid

• Never use bolus dosing of sedatives or opioids: causes hemodynamic instability and compromised cerebral perfusion 4, 3
• Never implement daily sedation interruption protocols in patients with radiological signs of high ICP 1, 2
• Never delay vasopressor use while attempting fluid resuscitation alone in hypotensive patients 4
• Never use hypotonic fluids (Ringer's lactate, Ringer's acetate, gelatins): only 0.9% saline is isotonic by osmolality 1
• Never assume opioids are contraindicated: uncontrolled pain increases ICP and metabolic stress 4
• Never use high-dose barbiturate "coma" routinely: reserved only for refractory ICP with preserved CO2 reactivity 7
• Never use propofol for pediatric ICU sedation in head injury due to increased mortality risk 3